An ascitic murine tumor, embryonal ovarian cell carcinoma, was used as a model of human ovarian carcinoma restricted to the peritoneum. The tumor was treated with a combination of hematoporphyrin derivative and intra peritoneal 514 nm light. Four HPD/laser treatments of 2 day intervals resulted in an 85% cure rate as determined by greater than 100 day survival (untreated mice die between 20 and 23 days following the introduction of the tumor). Toxicity studies of the HPD/laser treatment are being carried out on dogs as a preliminary step for treatment of human patients. The possibility of using singlet oxygen fluorescence as a method of dosimetry is being evaluated.